Thermostatic switch



9 G. HERBSTER 1,830,657"

THERMOSTATIC SWITCH Filed Aug. 22. 1929 INVENTOR. 7C 2 M x/./ m

. A441 ATTORNEY.

Patented Nov. 3, 1931 PATENT OFF-ICE GEORGE HEBBS'I'EB, OF CLEVELAND,OHIO THERMOSTATIC SWITCH Application filed August 22, 1929. Serial No.387,629.

My invention relates to thermostatic electrical switches and moreparticularly to such devices designed for use in connection withhousehold. electrical appliances.

It is well known that many pieces of-household electrical equipment areruined by overheating, short circuits and such, and quite often firesresult from misuse of such equipment by non-technical operators.

Furthermore, most of such equipment is now provided at such low costthat no great ex nditure is warranted in providing it with sa etycontrols, especially as such must be not only small and neat inappearance but also inexpensive, simple in construction and adjustment,yet capable of functioning properly under very adverse conditions ofcare and use.

It is an object of my invention to eliminate the dangers mentioned byproviding a thermostatic electric switch which will meet allrequirements demanded in operation, yet

which is so constructed that it may be manufactured at a very smallcost.

Another object of my invention is to insure quick operation of athermostatic switch byproviding a switch which may be used at any placein the electric circuit and near to the source of the heat.

Further. objects of my invention will become apparent from therfollowingspecification, in which reference is made to the accompanying drawings,'the same reference nu-' merals'being used to designate the same parts inthe various views.

In the drawings Fig. 1 is a perspective view of my invention with theouter shell and part of the core slightly removed for clearness ofillustration.

. Fig. 2 is a plan view of a part of the central insulating core.

Fig. 3 is a side elevation of the element shown in Fig. 2. 4.5 Fig. 4 isa vertical longitudinal section showing a modified form of my invention.

Fig. 5 is a horizontal longitudinal section of the form shown in Fig. 4.

Referring to the drawings, I provide a conductor -1 in the form of ametallic strip, prefwhich slides tightly over erably of brass, to whichis connected a conductor 2 of an electrical circuit. This strip ismounted in an insulating core 3, a convenient form of which isillustrated and comprises two or more complementary sections, such as 4and- 5. The sections a and 5 are preferably formed of a substancecapable of resisting high temperatures, such as for instance, acomposition including lava as its principal ingredient. The thermostaticswitch may thus be positioned close to a source of high temperature suchas a flame, or an electrical resistance without danger of injuring thematerial or causing it to become softened or deformed. A suitable meansof securing this strip in the core is by complementary grooves 6 and 7and 8 and 9 of the core sections 4 and 5, respectively, into which thecontact strip is seated. This is clearly shown in Fig. 1.

A composite bimetallic bar suitably secured at one end as by fitting itinto complementary grooves 11 and 12 of the core sections 4 and 5,respectively, provides the thermostatic element 10. The stationary. endof the thermostatic element is connected to an electrical conductor 13of a normally closed circuit. The other end is freeto move toward andaway from the contact strip 1. The thermostatlc element is placed in thecore with the more expansible of the two materials on which it iscomposed, toward the contact strip 1, so that, in response to a rise intemperature, it is deflected away from the contact strip 1, to break thecircuit, and in response to a drop in temperature moves toward theclosed circuit position.

A suitable contact point 21 maybe provided near the end of thethermostatic element and an adjusting screw 22 on the conductor 1, sothat the range of operation of the two may be varied or regulated. Asuitable means for securin the sections of the core in their properpositions includes a shell 20 of any suitable heat conducting materialthe assembled sections of the core.

Shoulders let-and l5and 17, may be pro- Nided on the conductor 1, andthe thermostatic element 10 respectively, to secure them against axialmovement in the core. Likewise for neatness in appearance and additionallockin of these members in place, a ortion towar the ends may be offsetand t e 'cor respondin grooves formed in the core set at an ang e to theaxis, so that the ends of the contact strip and the thermostatic element10 project centrally from opposite ends respectively of the core. 7

It is desirable to rovide an opening 23 in the shell 20 throug which ascrew driver or other implement may be inserted to turn the adjustingscrew. The sections 4 and 5 my invention, in which both connections withthe external electric circuit are at one end of the thermostat. In suchcase the shell 20 may be closed at one end, as illustrated in Figs. 4and 5 at 30. In this form of my invention the grooves for supporting oneend of the contact and thermostatic elements are formed in one end ofthe core sections, the other end of the conductor being supported in agroove in the other end of one of the sections, as before described. Inother respects this form of my invention is similar in form and functionto the first described form.

The thermostatic switch is located in an electric circuit at any pointwhere it is desired to control the range of temperature, as, forinstance, when used with an electric iron or heater, it may be attachedto the same where it will respond to the temperatures of such'devices.When cold the thermostat element is bent toward and into contact withthe conductor 1, closing the electric circuit. If, however, thetemperature near the thermostat exceeds a predetermined degree, thethermostatic element responds b moving away from the conductor 1 to breathe electric circuit, and thus deenergize the device connected in thecircuit. By adjusting the screw, the thermostat can be made to operateover a wide or narrow range of temperature changes.

It will be apparent by my invention that a thermostatic electric switchof this type may be manufactured at a very small cost because of itsextreme simplicity of construction which permits the parts to be formedfrom standard stock by simple stamping and molding operations. Theconductor may be read- 11y stamped from sheet material, while thethermostatic element may be stamped from strips of compositethermostatic materials. The core sections 4 and 5 may readily be moldedfrom a single mold likewise and the slots 6, 8, 11 and 12 subsequentlycut in, or these arts may be molded separately in simple mo ds and theslots formed in the molding thereof. The section shown in Fi s. 4 and 5may also be readily molded. e shell 20 is cut from standard tubing stockof suitable diameter.

While I have described my invention as desirable for use with householdelectric a pliances, it is not my intention to so limit its use, but toinclude an and all uses to which it may be adapted. arious changes maybe made in the details of construction and ar- Tangement of partswithout departing from the spirit of my invention or the scope of theappended claim.

I claim: V

In a thermostatic electric switch, a heat conducting shell, a core inthe shell having separable complementary portions and having an axialopening therein intermediate its ends, the complementary portions ofsaid core having cooperatin slots therein, a rigid conductor extendingte full length of the opening in the core and having its ends seated incertain of said slots, means to prevent lon itudinal movement of theconductor in t e core and a thermally responsive conductor having aportion seated in the cooperating slots in one end of the core andhaving its other end extending into the open the core for movementtherein in respci :1 variation in temperature, said tb sponsiveconductor being and away from said rigid conductor to and break anelectric circuit through the con" ductors.

In testimony whereof, I hereunto ai'iix signature this 10th day of Auust, 1929.

. GEORGE H RBSTER.

